Research on Resistance and Flow Characteristics of 7-Rod Bundles with Simple Support Grid at Reynolds Numbers of 1000-10000

Abstract

The grid positioning triangle fuel assembly is a potential fuel design form in the fourth generation reactor, especially in lead/lead bismuth reactors. Although different from the critical heat flux strengthening brought about by the complex form of PWRs grids, it is still necessary to study the resistance and flow characteristics of liquid metal in lead bismuth fuel assemblies with simple support grids, in addition to their positioning role. Due to the opacity of liquid metals, this study adopted the particle image velocimetry (PIV) and refractive index matching (RIM) method, utilizing the similar flow characteristics of water as working fluids at the same Reynolds number to conduct experiments and measured resistance characteristics. The influence of simple support grids on velocities, as well as the resistance characteristics of simple support grids, were studied in the range of Reynolds numbers from 1000 to 10000. The results show that, the SST k-ω turbulence model in CFD showed consistency with PIV experimental measurements over a wide range of Reynolds numbers, making this turbulence model more applicable. And the simple support grid resistance characteristic has been studied, a new grid CV expression has been obtained. The research results can provide support for the calibration or model improvement of the fourth generation fast reactor subchannel code and CFD tool.